Means for compensating for fluid loss in hydraulic transmission systems



9 7 8, 3 m auf Z 2 f E @M1 2 m ,L E 0 iy Lm R n 5 )\)\l m/ W E EN L V A MEA N Lmm w s M 8 L 1 1\/\\./|\|/\ E ARN@ 00 6 W F IH O www@ u 4 W w m am f S 1 mmm W.. 0 E .M M n mw M ,f f M MCM HMTM o L w N V Gwmm M y/ H A B 4 V m 7 m 4mm 7 vit/LVM Am 4 j m lllLV/ w Feb. 6, 1951 Patented Feb. 6, 1951 LGSS IN SYSTEMS HYDRAULIC TRANSMISSIGN" Carl Ga Hebel, Leonia, and Ernest A. Crawfordt Cliifside Park, J., assignors to Sperry Products, Inc., Hoboken. N. J., a. corporation ofNew York Application: May2`5, 1946', Serial No; 6724195" l Claim..

This' invention. relates H to hydraulic. controls ofthe type wherein` movements of a transmitter are reproduced by a. receiver throughthe medimm of a luid connection.. MoreI particularly, the invention relates to` 2-pipey hydraulic. systems. wherein fluid` is moved in` one. direction betweenatransmitter and receiver,` and in the opposite direction between., receiver and transmitter. In such systems, both. thetransmitter and the receiver are ofthe double-acting variety in which, two` mechanically separate but functionally inter-related hydraulic systems are present, each system` including one of said pipes and so arranged that movement of fluid in one pipe in a givendirection causes movement oi. the` fluid in the other pipe the opposite direction.

In closed systems of the. above type, the problem arises of relieving; the pressure in the system upon rise temperature, and of compensatinigf` for the variable volume of liquid due to temperature variation. and leakage. Heretofore, theY method employed to solve this problem consisted in provingA each separate hydraulic system (each of the twor sides of a` double-acting, closed: systen'i)` with a reservoir under pressure, and the transmission; of power was effected against the higher. pressure existing in the respective reservoirs.' Several undesirable results followed. from. the use of this arrangement.

In th-e first place7 since each side was provided 5 with its own reservoir, leakage or temperature variation in one side, different. from. the lealrage or temperature, variation in the other side caused loss of synchronism between the. transmitter and the receiver;` In the second place, since the` pressure the: reservoir determined the force which could be transmitted and received, any leakage or temperature variation which. varied the pressure in. the respective reservoii` also varied the output` from the transroitter.

It is, therefore, one of the principal objects of tina invention to provide pressure release and voiunrecompensation in a 2-way hydraulic control' of the: type described.A wherein the necessary correction will be. madev automatically without affecting the capacity oi' the transmitter and the receiver and independent oi? the pressure in the reservoir.

it is a further object of this invention to provide pressure release and fluid volume cornpensating means in which a single reservoir may he employed for both sides of the 2-way, Z-pipe hydraulic control.

Itis. a further object to provide pressure release and duid volume compensating means. for a. plurality oi Zepipe. hydraulic controls in coinbination with. a single reservoir.

It is a further object of this invention to provide compensating meansy wherein slow leaks on either side of. a 2lpipe hydraulic control will not. cause loss oi' synchronsm. between trantrnitter and receiver.

Still. other objects and advantages ot this invention will become apparent in the following detailed descriptiony thereof- In the accompanying drawing.,

The figure is. a- `front elevation. of an` assembly, partl-,z sectioned vertically' oi. one embodiment this invention.. i

Referring to. the drawing., the invention is shown as applied to a Q-pipe hydraulic control comprising a transmitter cylinder It!) within which` operates a. piston il connected by. rod I2 to. a transmitter handle l5 pivoted for. movement. at [El 'Ehe control also comprises receiver cylinder 2c within;` which operates aY piston. Ztl connectedl by` rod 22 to. al receiver,l or operated, member 2.5 pivoted for movement at 2t.. The pistons il.. and. il! divide. the` cylinders intoY two separate chambers.. and corresponding. cham.- bers ot the. cylinders are connected pipes 2.1 and iiso that two-i separate hydraulic systems are formed on opposite sides ot. the pistons. The systems are howeven functionally interrelated whereby movement of ii-uidin one system in one direction causes movementI of fluid in the other system inthe opposite direction.

The two! separate hydraulic` systems arel iilled with. liquid,l giving rise to the.f problem set forth in the introduction heretor of providing pressure release and. of compensating-for changes in volurne-offl-iquid dueto temperature variations and leakage. One solution which avoids the objectiene present in systems heretofore7 employed is shown-` the' drawing. In' this form of the invention, a single reservoir 3.8i is= employed and thisreservoir is adaptedlto be connectedY tof both hydrauiic' systems` e., both side'siof the 2-way, Z-pipe hydraulic control)l by way of al compensating valve' member 4ty and connections M and to the respective hydraulic systems` at oppositesides of! the` control. Thereservoir 3ER is at atmospheric pressure, if vented, or at higher than atmospheric pressure, if pressurized. Within the valve member 40 is a sliding valve iii havingports 46, 4l cooperating with connection 4i, and having ports 48, 49 cooperating with connection 42. The ports 46 and 48 selectively are connected to the reservoir by way of ports 55 and 5i which are so positioned that only one port 45 or 48 can cooperate with its respective port t or 5l at a time. The higher pressure in one side of the hydraulic control will cause the sliding valve 45 to be moved toward the lower A pressure side until it strikes stop 52 or 53. In this position the reservoir is connected to the low pressure side. Thus, if the handle l5 is operated to move piston Il to the right, pressure will be increased in the pressure system at the right of pistons Il and 2| and connecting pipe 28. Pressure will be increased in pipe 42 and the right hand end of valve member 4B, to move the valve 45 to the left until port 45 registers with port 5i! to connect the reservoir to the'low pressure side through pipe 4l and the pressure system to the left of pistons H and 2| and pipe 2l. Similarly, movement of handle l5 to the left, will move piston l l to the left and move sliding valve 45 to the right, to cause ports 48 and 5l to register, to connect the reservoir to the low pressure (now the right hand) system of the control.

It will be observed that the passages 55 and 5! are positioned further apart than ports 45 and 48. This means that only one of these ports can register Awith its respective passage at any one time. Furthermore, the distance between passages 5i] and 5l is sufiiciently greater than the distance between the seals forming the inner boundaries of ports 48 and 4X5 so that when one of these ports moves out of registry with its respective passage a certain degree of movement of the valve body will take place during which neither port registers with its respective passageway. YIn this manner it is impossible for both ports to be even partially in Aregister with their respective passagewavs at any one time, and therefore it is impossible to transfer liquid from Vthe hydraulic system at one side to the hydraulic system at the other side. This' is an eX- tremely important feature in such applications as contemplated here where precise synchronisrn between the transmitter and the receiver elements is essential. If at any time even momentary connection were made between the hydraulic systems at the two sides, then obviously. there would be a greater or less loss of synchronism which in those applications dependent upon exact synchronism would be so undesirable as to render the device inoperative.

Since there is normally a connection between one side (or pressure system) and the reservoir, pressure release and volume compensation are thus assured. A connection 5'! directly between the pressure systems which short circuits the valve member 4i! permits synchronization by means of valve 58. Changes in temperature will result in a displacement in the relative positions of handle I5 and lever 25 dependent upon the position of the movable valve body.Y The position of the movable valve body is at any time dependent upon the direction of force last applied to the handle 15. If the number of times that the handle l5 is moved from right to left is equivalent to the number of times it is moved in the reverse di- '4 rection, which is essential, and there are several such movements during the period oi. temperature change, then deviatons in one direction will compensate for those in the other direction and thus maintain the system `in substantial synchronization. For unusual conditions when the system may be left in one position for an extended period of time during which temperature changes occur the synchronizing valve 58 is provided which may be used for synchronizing the handle and lever at either end of the stroke or at any intermediate position if the position of lever 25 is known. This would be of consider-V able advantage in aircraft where it is desirable to synchronize at full throttle in night and at closed throttle on the ground and in power boats where it would be desirable to synchronize at full throttle under pursuit conditions and closed throttle when maneuvering in harbors or controlling gears, clutches, etc.

The foregoing description of the invention is 4merely illustrative and changes may be made 'within the scope of the appended claim.

Having described our invention, what we claim and desire to secure by Letters Patent is:

In a hydraulic control, a double-acting transmitter, a double-acting receiver, iiuid transferring connections between the respective sides of the transmitter and the receiver whereby separate hydraulic systems are formed on opposite sidesof the control, a reservoir, means including a Valve whereby said hydraulic systems may be selectively connected to and disconnected from the reservoir when the transmitter is actuated, said last named means comprising astationary valve casing and a movable valve body, uid connections between the pressure systems and opposite sides of the valve body whereby the valve body will be moved in response to the pressure in the higher pressure hydraulic system. said casing having a plurality of passages communicating with the reservoir, said valve body having a plurality of ports adapted to cooperate with the passages in said casing, the distance between ports being different from the distance between passages by an amount such that only one port can register with its respective passage at any time, the dierence in distances between ports and passages being also suiiicient so that the second'port cannot register with its respectiv-e passage until the rst'port has passed a predetermined distance out of register with its respective passage, whereby no fluid can pass between the hydraulic systems.

CARL G. HEBEL. ERNEST A. CRAWFORD.

REFERENCES CITED The following references are of record in the le Yof this patent:

UNITED STATES PATENTS Number Name Date 2,014,338 Messier Sept. 10, 1935 2,361,774 Koons a Oct. 31, 1944 FOREIGN PATENTS Number Country Date 606,576 France Mar. 12, 1926 

